Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

h,w = map(int,input().split())
maze = [input() for _ in range(h)]

gx, gy = w-1, h-1

q = deque()
q.appendleft([0,0])
INF = 10**5

dist = [[INF]*w for _ in range(h)]
dist[0][0] = 0

while q:
  x,y = q.pop()
  
  for dx,dy in [[1,0],[0,1],[-1,0],[0,-1]]:
    nx = x+dx
    ny = y+dy
    
    if 0<=nx<w and 0<=ny<h:
      if dist[ny][nx]==INF and maze[ny][nx] != '#':
        dist[ny][nx] = dist[y][x]+1
        q.appendleft([nx,ny])      

black_num = sum([maze[i].count('#') for i in range(h)])

if dist[gy][gx] == INF:
  print(-1)
else:  
  print( h*w - dist[gy][gx] - black_num -1 )